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Mattermost ServerApplication · Mattermost

CVE-2025-35965

HIGH · 7.5 CVSS v3.1 Published 2025-04-24
Fix available
A fix is available. Upgrade to 9.11.11 / 10.4.3 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Mattermost versions 10.4.x <= 10.4.2, 10.5.x <= 10.5.0, 9.11.x <= 9.11.10 fail to validate the uniqueness and quantity of task actions within the UpdateRunTaskActions GraphQL operation, which allows an attacker to create task items containing an excessive number of actions triggered by specific posts, overloading the server and leading to a denial-of-service (DoS) condition.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Mattermost fails to validate the uniqueness and quantity of task actions in the UpdateRunTaskActions GraphQL mutation, allowing attackers to create unbounded numbers of task actions tied to posts. This exhausts server resources and causes denial of service.

MitigationUpgrade to Mattermost versions 10.4.3, 10.5.1, 9.11.11 or later. As interim mitigation, implement rate limiting on the GraphQL endpoint or temporarily restrict GraphQL API access.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Mattermost ServerApplication
Affected:>= 9.11.0, < 9.11.11>= 10.4.0, < 10.4.3= 10.5.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Mattermost Server version
    Run 'sudo mattermost version' or check the System Console under About > Mattermost, or inspect the /opt/mattermost/version.txt file
    Affected if The installed version falls within >= 9.11.0 and < 9.11.11, OR >= 10.4.0 and < 10.4.3, OR equals 10.5.0
  2. Confirm GraphQL API is enabled
    Check the Mattermost config.json for 'ServiceSettings.GraphQLEnable' setting, or navigate to System Console > Experimental > Features and verify if GraphQL is toggled on
    Affected if GraphQL is enabled and accessible to the user role in question
  3. Identify unusually high task action counts
    Query the database: 'SELECT PostId, COUNT(*) as action_count FROM PluginKeyValueStore WHERE PluginId LIKE "%tasks%" GROUP BY PostId HAVING COUNT(*) > 50;' or inspect posts in the UI for excessive task action buttons
    Affected if A specific post has more than a reasonable number of task actions (normal is typically single digits)
  4. Check for resource exhaustion indicators
    Monitor server CPU, memory, and database connection usage during GraphQL API calls, or review mattermost.log for timeout or slow query warnings related to task actions
    Affected if Server resources spike during UpdateRunTaskActions GraphQL calls or database queries become unusually slow

You are affected if your Mattermost Server version is one of the vulnerable releases AND the GraphQL API is enabled, allowing unauthenticated or authenticated users to invoke the UpdateRunTaskActions mutation and create excessive task actions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 9.11.11 / 10.4.3 or later
Fixed in 9.11.1110.4.3
Interim mitigation

Upgrade to Mattermost versions 10.4.3, 10.5.1, 9.11.11 or later. As interim mitigation, implement rate limiting on the GraphQL endpoint or temporarily restrict GraphQL API access.

Recommended fix High confidence

Upgrade to 9.11.11, 10.4.3, or 10.5.1 (or later stable release) depending on current version

  1. 1. Identify current Mattermost Server version by checking the System Console > About page or running 'mattermost version'
  2. 2. For version 9.11.x (9.11.0 through 9.11.10): Upgrade to version 9.11.11 or later
  3. 3. For version 10.4.x (10.4.0 through 10.4.2): Upgrade to version 10.4.3 or later
  4. 4. For version 10.5.0: Upgrade to version 10.5.1 or later
  5. 5. After upgrade, verify the server is running the fixed version and monitor for any anomalies
Caveat Review release notes for any configuration or behavioral changes between versions; test in staging environment before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing5.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,970
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-35965 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data